When homogeneous combustion is performed during a cold start in a direct injection engine by injecting fuel in the intake stroke, the three-way catalyst is not activated, and hence HC is discharged without being reduced. JP2000-145510A, published by the Japan Patent Office in 2000, discloses a technique to prevent this by detecting the engine temperature, and injecting fuel in the compression stroke at an air-fuel ratio that is regulated to the lean side of the stoichiometric air-fuel ratio when the detected temperature is lower than a predetermined temperature.
According to this technique, the amount of fuel that adheres to the wall surface of the cylinder during a cold start can be reduced, and the amount of air-fuel mixture flowing into the quench zone during stratified charge combustion can also be reduced. Moreover, the exhaust gas temperature rises, thus accelerating the oxidation reaction of the HC in the expansion stroke, and hence an overall reduction in the amount of HC can be achieved.